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Astron. Astrophys. 336, 359-366 (1998)


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The study of magnetic field configuration of a 1N/M1.1 flare in AR7321

Wang Tongjiang 1, Qiu Jiong 2 and Zhang Hongqi 1

1 Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, P.R. China (e-mail: wtj@sun10.bao.ac.cn)
2 Department of Astronomy, Nanjing University, Nanjing 210093, P.R. China

Received 30 September 1997 / Accepted 30 April 1998

Abstract

The present paper is aimed at reconstructing the magnetic configuration in an active region. The temporal evolution and spatial correlation of the magnetic features deduced from the photospheric observations have been investigated. Specifically, we have studied the non-potentiality in terms of new emerging flux, the vertical current system inferred from the photospheric vector magnetograms, and the distribution of magnetic free energy in the active region. We include a comparison between the magnetic connectivity patterns and the multi-waveband observations of a 1N/M1.1 flare in order to recover a comprehensive configuration from the photosphere up to the corona. The major results of this paper are: 1. the magnetic flux emergence considerably complicates the magnetic field with strong shear and enhancement of the vertical current system on the eve of the occurrence of the 1N/M1.1 flare. 2. The emerging bipole and some other pre-existing magnetic connection patterns, discovered from the photospheric observation, are identified with the flaring loops observed in the chromosphere and corona. 3. The footpoints of the flaring loops are located around the vertical current concentrations, indicating that they are perhaps current-carrying loops. 4. The emerging small loop interacts with the nearly paralell overlying long loop, which initiates the onset of the flare. Further energy release is triggered along the small loop, especially at the two foot regions, where the magnetic free energy is concentrated.

Key words: Sun: activity – Sun: flares – Sun: magnetic fields

Send offprint requests to: T. Wang

© European Southern Observatory (ESO) 1998

Online publication: July 7, 1998

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